Adsorption is the process of binding and removing certain substances from a solution through the use of an adsorbent. Activated carbon is a commonly used adsorbent in the treatment of water, municipal wastewater, and organic industrial wastewaters, and it is typically used in powdered or granular form.
U.S. Pat. No. 7,972,512 describes a system that treats industrial waste water that includes oils, such as from refineries, utilizing GAC. The treatment system exposes the wastewater to the GAC in an aeration tank that is upstream of biological membranes. Advantageously, the GAC is held back from gaining entry to the membranes by screens. Upon being exhausted in its capacity to adsorb organic compounds, the GAC becomes “spent.” The spent GAC is removed from the aeration tank via a discharge port and fresh GAC material is introduced into the system in its place. The spent GAC may be disposed of, or may be transported offsite to be regenerated (reactivated) by removing the adsorbed organics, typically with a thermal process such as wet air regeneration (WAR) or in a reactivation furnace.
Other water treatment systems are known that utilize activated carbon without biological membranes. Such systems may circulate water to be treated through a GAC column or canister. Spent GAC columns or canisters are removed from the system and is either discarded or transported to a reactivation facility.
Spent GAC is typically regenerated at high temperature in a furnace. It is also known to regenerate GAC using chemical reagents, ozone or wet air oxidation. A concern when regenerating granular material is to limit the degradation of the particle size range caused by the regeneration process.